Wireshark-users: Re: [Wireshark-users] Fwd: sequence number and packet id
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From: Guy Harris <guy@xxxxxxxxxxxx>
Date: Sat, 12 Apr 2008 12:44:12 -0700
Fabiana moreno wrote:


thanks but i did some research already about the subject...
this is what i found...

http://www.freesoft.org/CIE/RFC/1889/9.htm

sequence number: 16 bits
    The sequence number increments by one for each RTP data packet sent,
    and may be used by the receiver to detect packet loss and to restore
    packet sequence. The initial value of the sequence number is random
    (unpredictable) to make known-plaintext attacks on encryption more
    difficult, even if the source itself does not encrypt, because the
    packets may flow through a translator that does. Techniques for
    choosing unpredictable numbers are discussed in [7].
So i might be wrong, but i dont think sequence number represent how much data is being sent.
He was probably referring to the TCP sequence number. You were referring to the RTP sequence number. Those are two different sequence numbers; I suppose that one could infer from the reference to the Darwin Streaming Server and from your earlier mails that you were referring to RTP, but it's really best to indicate what protocol you're talking about. 

Now:


     > I am streaming with darwin streaming server and capturing with
     > wireshark, i just wanted to know if what i am getting in my
    captures as
     > sequence number is my packet id?
to what "packet id" are you referring? (As per your previous mail with "packet id 0 ???" as the subject, the RTP sequence number is not required to be connected with the IP Identification field; they're independent fields.)